Bioavailability, in vitro Solubility, and Physical and Chemical Properties of Elemental Iron Powders

Abstract

Abstract The relative biological value (RBV) for rats of the iron from 7 elemental iron powders (produced by electrolysis, reduction with hydrogen (H2), carbon monoxide (CO), and desiccated ammonia (NH3), and carbonyl process) were compared with the in vitro solubility of the iron powders in 0.2% HC1 (w/v, ca 0.05/V) for periods of 5 to 90 min. The values obtained for per cent solubility in 10 min were within the fiducial limits of the individual RBVs of 6 iron samples; the exception was one preparation of carbonyl iron whose solubility, but not RBV, was as high as that of electrolytic iron. These data indicate that dissolution rates were good predictors of bioavailability of some types of elemental iron powders. There was good agreement between specific surface areas and particle size distributions of discrete fractions containing fine particles of comparable sizes (7—10 μm) of electrolytic, H2- and CO-reduced iron, and whole preparations of carbonyl iron, but these measurements were not satisfactory criteria for predicting bioavailability. SLOWPOKE neutron activation analysis of the iron powders showed that the carbonyl iron samples contained the lowest concentrations of elements producing short- and long-lived radioisotopes (24Na, 27Mg, 49Ca, 38Cl, 28A1, 66Cu, 56Mn, 52V, 101Mo, 51Cr, 122Sb, and 60Co) with the exception that the Mo content of one preparation was ca 2 times higher than in the other iron samples. Electrolytic iron contained higher levels of Na, Ca, Al, Cu, Mn, V, Sb, and Co than carbonyl iron. H2-, CO-, and NH3-reduced iron samples contained the highest levels of impurities, notably Na, Mg, Ca, CI, Al, Cu, Mn, V, and Cr.